This invention pertains to the art of methods and apparatuses for the production of pneumatic tires, and more specifically, to methods and apparatuses for a self-locking mold cure system.
It is well known in the art to cure, i.e., vulcanize, green tires using a tire press. Typically tire presses use molds comprising top and bottom mold halves, within which the green tire is cured. The tire press includes devices for opening the mold, that is, lifting the top mold half from the bottom mold half, loading the green tire into the bottom mold half, and closing the top mold half upon the bottom mold half, thereby encasing the green tire within the tire mold. Heat mediums, such as steam, are then transferred to the mold from the outside of the mold as well as from the inside. A tire bladder is inserted inside the mold and the green tire and is used both to cure and to shape the green tire. Once the green tire is cured, the tire press then opens, that is, lifts the top mold from the bottom mold, revealing a cured tire which is then unloaded from the tire press. This cycle can be repeated as often as required.
One of the problems with this conventional type of tire press is that many devices are underutilized. The mold closing device, for example, closes the mold then sits idle while the green tire is cured. Only after the green tire is cured and unloaded and another green tire is loaded can the mold closing device be used again. The mold opening device, the green tire loading device and the cured tire unloading device are similarly underutilized. This means that the capital resources necessary for such tire presses are not being economically used.
Many attempts have been made to reduce these problems. For example, U.S. Pat. No. 3,932,079 to Legostave et al., discloses a tire vulcanizing apparatus that includes a series of vulcanizing presses arranged in a row. In short, Legostave et al. disclose an attempt at using a conventional tire press and moving it along rails over a line of tire molds. One of the problems associated with this apparatus are that the molds cannot be treated individually, but only in couplets of two. Another problem is that there is no provision for an independent loading device or a take-away conveyor. What is needed is a more flexible tire curing system.
U.S. Pat. No. 4,728,274 to Siegenthaler discloses a tire curing apparatus in which a number of mobile curing units are selectively moved along a loop circuit. This leads to a complex transport system for the mobile curing units.
U.S. Pat. No. 5,622,669 to Dailliez et al. discloses a tire vulcanization apparatus in which tire molds are transferred from a loading/unloading device into a chamber that receives several tire molds. The loading/unloading device is stationary. This apparatus makes it difficult to cure tires having different cure cycle times.
European Patent Application EP 0 510 332 A2 describes a mold changing apparatus including a row of mold stations, a moveable manipulator, and a mold preparing station provided within the row of mold stations. To use this apparatus, each mold must be carried by forklift or crane to each mold station. The manipulator combines the functions of opening/closing molds and loading/unloading tires. This combined use leads to operational inefficiencies.
The present invention provides methods and apparatuses for curing tires using a self-locking mold cure system with shared mold open, unload, load and close devices. The difficulties inherent in the art are therefore overcome in a way that is simple and efficient, while providing better and more advantageous results.
The invention relates to a tire curing system having a plurality of molds comprising loading means for loading green tires into a bottom half mold, mold closing means for placing a top mold half over the bottom mold half, self-locking means for locking the top mold half to the bottom mold half, curing means for curing the green tires, mold opening means for removing the top mold half from the bottom mold half, unloading means for unloading cured tires from the bottom mold half and take-away means for taking the cured tires away from the curing system.
The loading means and the unloading means include a moveable robot. The mold closing means and the mold opening means include a moveable manipulator, and movements of the robot and the manipulator are in a straight line.
The invention also relates to a method for curing a first green tire using a curing system having four horizontally spaced parallel process lines with a plurality of stations along each process line. Each of the four process lines has the same number of stations. The four process lines include a manipulator process line, a mold load-unload process line, a robot tire handling line, and a green tire delivery process line. The method comprises the steps of:
depositing the first green tire at a first station on the green tire delivery process line;
moving a robot along the robot tire handling line to a first station on the robot tire handling line;
moving a manipulator along the manipulator process line to a first station on the manipulator process line;
lifting a first top mold half from a bottom mold half positioned at the first station on the manipulator process line with the manipulator;
moving the first bottom mold half to a first station on the mold load-unload process line;
placing the first green tire on the first bottom mold half with the robot;
moving the robot along the robot tire handling line as required;
moving the first bottom mold half to the first station on the manipulator process line;
placing the first top mold half onto the first bottom mold half with the manipulator;
moving the manipulator along the manipulator process line to other stations as required;
vulcanizing the first green tire into a first cured tire;
moving the manipulator along the manipulator process line to the first station on the manipulator process line;
lifting the first top mold half from the first bottom mold half with the manipulator;
moving the robot along the robot tire handling line to the first station on the robot tire handling line;
moving the first bottom mold half to the first station of the mold load-unload process line;
removing the first cured tire from the first bottom mold half with the robot;
moving the first bottom mold half to the first station on the manipulator process line; and,
placing the first cured tire on a take-away conveyor with the robot.